Such sensor systems are often used for determining the relative humidity, for instance, in automotive air conditioners, in household appliances or in copier machines, and are consequently used in great quantities. As a cost-effective type of construction for the sensors used therein, so-called thin-film sensors are often used, whose functioning method is based, for example, on a capacitive measuring principle. The thin-film sensors are usually produced in planar fashion, i.e., all active films or layers as well as the contacting areas of the thin-film sensors are accommodated on one surface of the thin-film sensors. Generally, no coatings are then located on the back side of such thin-film sensors.
To manufacture a functional sensor system in as automated a manner as possible, printed circuit boards are fitted with these sensors and appropriately electrically contacted.
European Published Patent Application No. 1 046 030 describes a sensor system of this kind, the sensitive region of the sensor being disposed at an opening in the printed circuit board. This type of construction may have the disadvantage that, during operation of the sensor system, both sides of the printed circuit board are constantly exposed to the humidity to be measured. Moreover, additional production costs may result from the provision of the opening in the printed circuit board.
U.S. Pat. No. 4,942,364 describes a resistively acting moisture sensor, in which the moisture-dependent electrical resistance of a suitably prepared non-woven material is determined. This moisture sensor has two connecting wires for insertion into an electric circuit. The connecting wires are bonded to the non-woven material with the aid of a conductive adhesive. Such sensors may have the disadvantage that they are not, or are just barely, suitable for automatic assembly on a printed circuit board.